Optical components made of synthetic quartz glass and a method for producing the same are known from WO 2009/106134 A1. The optical component has a glass structure which is substantially free from chlorine, oxygen defect sites and SiH groups (below the detection limit of 5×1016 molecules/cm3). Within a diameter of 280 mm (CA area), the component exhibits a mean hydrogen content of about 3×1016 molecules/cm3 and a hydroxyl group content of 25 wt. ppm.
For the production of the component, a SiO2 soot body is dried such that a mean hydroxyl group content of less than 60 wt. ppm is obtained in the quartz glass produced therefrom. Prior to vitrification, the soot body is subjected to a conditioning treatment including a treatment with nitrogen oxide. For reducing mechanical stresses, the quartz glass blank is subjected to an annealing temperature and is finally loaded with hydrogen in an atmosphere of 80 vol.-% nitrogen and 20 vol.-% hydrogen at 400° C. at an absolute pressure of 1 bar for a duration of 80 hours.
Due to the manufacturing process, the synthetic quartz glass produced in this way contains nitrogen, which is chemically bound in the glass network. It shows an advantageous damage behavior vis-à-vis shortwave UV laser radiation especially with respect to the so-called “compaction”.
With the damage behavior of the “compaction”, a local increase in density is observed in the volume penetrated by radiation during or after high-energy UV laser irradiation of the glass. This causes a local increase in the refractive index which is progressing during continuous irradiation and thereby leads to an increasing deterioration of the imaging properties of the optical component and, in the end, to a premature failure of the component.
For the sake of simplicity, the changes in the refractive index distribution due to compaction are often determined not at the applied wavelength, e.g. at 193 nm, but by using a Fizeau interferometer equipped with a helium-neon laser with a measurement wavelength of 633 nm (more exactly: at a wavelength of 632.8 nm).
It has now been found that, despite identical or similar measured values of their compaction at a measurement wavelength of 633 nm, quartz glasses can surprisingly show different damage behaviors at a measurement wavelength at 193 nm. This particularly poses problems whenever the quartz glass to be measured hints at a quite acceptable compaction behavior at a measurement wavelength of 633 nm, but, upon use with the applied wavelength, unexpectedly shows much poorer values or is even unusable.